(a) Field of the Invention
The present invention relates to a process and an apparatus for the production of an impure light gas by permeation, starting from a gaseous mixture. It is particularly applicable to the production of impure hydrogen starting from a mixture consisting essentially of hydrogen, nitrogen and hydrocarbons.
(b) Description of Prior Art
In some industrial applications, hydrogen is needed, which has a low purity, lower than that which may be obtained with simple permeators, i.e. having an inlet and two active outlets, namely a high pressure inlet, a high pressure outlet and a low pressure outlet.
To increase the hydrogen extraction yield while lowering its purity, it has been proposed to bypass a portion of the supply flow or "feed". It has also been proposed, for the same purpose, to use reflux permeators, instead of simple permeators, in which a portion of the residual gas is returned in the low pressure space in order to lower the partial pressure of hydrogen therein. These expedients enable to effectively increase the yield of extraction of hydrogen or, for a given yield, to decrease the investment, i.e. essentially the required surface of the permeation membrane.
The invention aims at increasing much more importantly the increase of extraction yield or of the investment.